Switching system



June 30, 1925.

v 1,543,688 R. S. WILBUR ET AL SWITCHING SYSTEM Filed Dec. 17. 1920 gQgQl-cgiifij W //7 ve/vfohs': Way 5? W/M aw. fayar ZZJo/mson.

Patented June 3%, i925.

UMETEE fiTATES is-ace rarnu'r er RAY S. JVILBUR, OF LYNDHURSTQAND LO. JOE-INSGN, G3? T GRAIQGE, HEW

TFiRD, 03? NEE] YORK, N. Y., A. CORPORATIGN OF NEW YORK.

SWITCHING SYSTEM.

Application filed. December 17, 1920. Serial No. 4315M.

To all whom 2'15 may concern:

Be it known that we, RAY S. YSTILBUR and EDGAR D. Jonnsorv, citizens of the United States, residing at Lyndhurst, in the county of Bergen, and East Orange, in the county of Essex, and State of New Jersey, respectively, have invented certain new and useful Improvements in Switching Systems, of which the following is a full, clear, concise and exact description.

This invention relates to switching systems and more particularly to such systems which are especially applicable to signaling on circuits composited for telephone and telegraph operation, and upon which telephone repeaters are installed.

On certain long distance telephone lines it is necessary or desirable, whereuthe physical character of the various sections of the line differ, or the operating conditions are not uniform, to use signaling current of different frequencies for each section, pro viding switching circuits for changing from current of one frequency to that of another. These circuits aregenerally known as composite ringer circuits.

For signaling over telephone lines upon which telegraph instruments are installed, it has been found that a current of 16 cycle frequency, whichis commonly used for local telephone signaling, is unsatisfactory since current of this low frequency may operate the telegraph instruments. Accordingly, it has been the practice to use current of a higher frequency, generally, 135 cycles per second, which current has noappreciable effect on telegraph operation.

In like manner on lines upon which repeaters are installed, where it is desirable to amplify the signaling current, it is preferable to use a current of a frequency higher than 135 cycles and within the voice fre quency range since repeater circuits are normally designed to amplify speech currents. Previous to this invention composite ringer circuits were used generally to change from 16 cycles to' 1351cycles at terminal points.

It is the object of this invention to'provide a composite ringer circuitadapted to change from current of frequency of 135 cycles, or of a frequency below the voice range, to a current- ,of frequency preferably within the voice range, and in this way secure an eflicient transmission of signaling current through a repeater circuit.

To attain this object in accordance with a feature of this invention, there is provided a circuit organization consisting of sending and receiving circuits for currents of fre-- quencies within and below the voice frequency tinge, respectively, and a i-wire repeater circuit. These circuits are properly interconnected to attain the object stated above.

' In accordance with another feature of the invention the object is further attained by the provision of a novel and efficient method of changing theconnec-t-ions of the repeater circuit upon the actuation of either sending circuit to avoid singing, and at the same time maintain an eflicient path for the trans mission of signaling current through the repeater circuit.

The nature of the invention will be more clearly understood from the following specification and the accompanying drawing in which the figure shows one embodiment thereof, in which there is shown placed between the two transmission lines, terminal apparatus, including certain circuits already known in the arts, which will be more clear ly comprehended from the following description.

The figure shows the outgoing end of a transmission line designed to operate with current of infra voice frequency and a transmission line E designed to operate with current within the voice frequency range. Between the ends of the transmission lines within the dotted lines, voice frequency sending and receiving circuits S and K, respectively, are shown. These circuits are essentially similar to those disclosed in the co-pending application of Paul E. Murphy, Serial No. 87 9,7 05, filed May 8, 1920. There is also shown. a i-wire repeater circuit-A similar to that disclosed in U. S. Patent No. 1,252,786, granted September 14:, 1920 to George A. Campbell and a composite ringer circuit having the essential features disclosed in U. S. Patent No. 709,437, granted September 16, 1902 to John M. Fell.

Signaling current of 135 cycle frequency incoming from the line W actuates a relay 1, which causes voice frequency current from the sending circuit S to be applied by a relay 2 to the line E through the repeater circuit A. At the same time a relay 3 operates and short circuits the transformer 5 at the input points thereby preventing the repeater circuit from singing. Signaling current incoming from the line E passes through the repeater circuit A and causes the receiving circuit R to respond. Relay 7 is actuated and switches 135 cycle current to the line TV. Simultaneously a marginal relay 4 responds and opens the output circuit of transformer 5, thereby preventing singing.

It is thought that the invention will be more clearly understood from the following detailed description of the operation of the system.

Assuming that signaling current of 135 cycle frequency comes in from the line W, it passes through the normal contacts of relay 7, the condenser 00, the windings of re-- tardation coils 8 and 9 and relay 1, the armature of which relay is set into vibration and opens an obvious circuit through the winding of the normally operated relay 10, causing the release of relay 10, and the operation, through an obvious circuit, of relay 11. The operation of relay. 11 likewise causes the operation of relays 2 and 12. When relay 12 operates it causes the operation of relay 13 by closing a circuit through the winding of relay 13 including the condense-r 14 and the source of low frequency ringing current 15. The operation of relay 12 also causes battery potential to be placed on lead 16 causing the vacuum tube oscillator circuit to generate voice frequency current. Each time relay 13 operates in unison'with the pulsations of ringing current it connects ground through its contact and condenser 17 to point 18 of the oscillator circuit, changing the tuning of the circuit. This results in two successive trains of current waves, each of a different frequency, being transmitted to the receiving circuit A through the upper and lower alternate contacts of relay 2.

- l Vhen relay 10 releases, due to the'operation of relay'l, relay 3, operates through a circuit extending from grounded battery, through the winding of relay 3, normal contact and winding of'relay 4, resistance 20, and contact of relay 10 to ground. Relay 3 short-circuits, through its contact, the out-. put circuit of the repeater X. Relay 4 however, obtains insufficient current in this circuit to operate.

The voice frequency signaling current passes from the'alternate contacts of relay 2 through windings 21 and 22 of the transformer 5, connected through the contact of relay 3. Current is accordingly induced in the lower coils of tra-nsforer 5 and passes through the two upper normal contacts of relay 4, and the repeater Y to the center points of the middle and lower coils of transformer 6. Current next passes to the line E and causes the response of a receiving circuit at the distant end which may be similar to circuit R.

The repeater circuit A is prevented from singing by the use of balancing artificial lines N and N as described in the above mentioned Campbell Patent No. 1,352,786. hen relay 2 operates however, artificial line N is no longer balanced, and singing would result were it not for the short-circuiting of the output circuit of the repeater Xby relay 3 as described above.

When a signal is received from a direction opposite to that assumed in the preceding description, voice frequency current of the proper character to actuate the receiving circuit R enters the repeater circuit A from the line E and passes through the middle and lower windings of transformer 6 and the artificial line N Current is induced in the upper winding of transformer 6, passes through the repeater X, the windings 21 and 22 of transformer 5, the normal contacts of relay 2 and the conductors 23 and 24 to the receiving circuit R. Relay 29 of the receiving circuit R thereupon operates causing the release of slow releasing relay 27. Relay 27 in releasing ope-rates marginal nelay 4 over a circuit extending from grounded battery, through the winding of relay 3, normal contact of relay 4, and the contact of relay 27 to ground. Relay 4 operates and locks itself up through a circuit including its at ternate contact and resistance 19 to grounded battery, disconnects relay 3 from the circuit initially traced, and disconnects at its upper normal contacts the lower winding of transformer 5, from the input circu of repeater Y.

When relay 27 releases, it also causes the operation over an obvious circuit of relay 7 which switches to the line WV, 135 cycle ringing current from a source 28. This current passes over the line TN and causes the response at the distant end of a receiving circuit including a relay 1, and other connected apparatus, similar to that shown.

The opening of the input circuit of repeater Y prevents the repeater circuit from singing, which would result because of the unbalancing due to the opening of the circuit at the normal contacts of relay 7.

What is claimed is:

1. In a signaling system, two sections of transmission lines, a four-wire repeater circuit associated with one section, terminal apparatus between the repeater circuit and the other section, a single conductor extending from the terminal apparatus to the repeater circuit, and means to control over said conductor the connections of the repeater circuit to prevent singing.

2. In a signaling system, two sections of t ansmission line,'a four-Wir p ater Gilcuit associated with one section, terminal apparatus between the repeater circuit and the other section, a single conductor extending from the terminal apparatus to the repeater circuit, relays in circuit with said conductor, and means for controlling the operation of said relays over said conductor to control the connection of the repeater circuit to prevent singing.

3. In a signaling system, two sections of transmission line, a four-wire repeater circu it associated with one section, terminal apparatus between the repeater circuit and the other section, a source of signa ling current of one frequency for transmission inward over the line through the repeater ci rc-uit, a source of signaling current of another frequency for transmission outward through the repeater circuit, means responsive to the second mentioned frequency for connecting the repeater circuit so as to prevent singing on outgoing signaling current, and means responslve to the first mentioned frequency to connect the repeater so as to prevent singing on incoming signaling current.

4. In a signaling system, two sections of transmission line, a four-wire repeater circuit associated with one section, terminal apparatus between the repeater circuit and the other section, said repeater circuit including an inner transformer connected to said terminal apparatus and an outer transformer connected to a line section, interconnections between the input and output points of the outer and inner transformers, respectively, and the output and input points of the inner and outer transformers, respectively, a conductor extending from said terminal apparatus to said repeater circuit, a relay in circuit with said conductor to open the output circuit of the inner transformer, a relay in circuit with said conductor to short-circuit the input circuit of said inner transformer to prevent singing of the 'epeater circuit, and means to operate each of said relays independently of each other over said conductor.

5. In a signaling system, two sections of transmission line, a four-wire repeater circuit associated with one section, two receiving circuits between said repeater circuit and one of said line sections, a conductor extending from said receiving circuits to said repeater circuit, a relay to change the repeater circuit connections to prevent singing upon the response of one of said receiv ing circuits, a second relay to change the connection of the repeater circuit to prevent singing upon the response of the other receiving circuit, and means to operate each of said relays independently upon the response of each receiving circuit.

6. In a signaling system, two sections of transmission line, a four-wire repeater circircuit associated with one section, said repeater circuit including an inner transformer connected to said terminal apparatus, two receiving circuits between said repeater circuit and-one of said line sections, a conductor extending from said receiving circuits to said repeater circuit, a relay in circuit with said conductor to ope-n the output circuit of the inner transformer, and a relay in circuit with said conductor :to short-circuit the input circuit .of said inner transformer to prevent singing of the repeater circuit, one of said relays being under control of the other, a locking circuit for the control relay, means for maintaing the .controlling relay operated independently of the other relay, and means for removing the latter relay from the operating circuit, upon the operation of the control relay.

7. In a signaling system, two interconnected sections of transmission line, a relay associated with one of said sections and responsive to current from that section to open the connection between said sections, a second relay associated with the other of said sections and responsive to current from that section to open the connection between said sections, a four-wire repeater circuit connected between the second relay and its associated section, a source of signaling current, and means separately responsive upon the actuation of each relay to change the connections of the repeater circuit to secure an efficient transmission circuit for signaling current from said source through the repeater circuit.

8. In a signaling system, two interconnected sections of transmission line, a relay associated with one of said sections and responsive to current from that section to open the connection between said sections, a second relay associated with the other of said sections and responsive to current from that section to open the connection between said sections, a four-wire repeater circuit connected between the second relay and its associated section, and means separately responsive upon the actuation of each relay to change the connections of the repeater circuit to prevent singing.

9. In a telephone system, a transmission line, a four-wire repeater circuit connected thereto, means for supplying current of a first frequency, means for supplying current of a second frequency, and means selectively responsive to the transmission of each of these currents over the line for changing the connections of the repeater.

10. In a telephone system, a transmission line, a four-wire repeater circuit connected thereto, means for generating current having a frequency F, means for generating a current having a frequency F, and means selectively responsive to the transmission of each of these currents over the line for nected there-to, devices connected between 2 automatically changing the connect-ions of the repeater circuit to prevent singing.

11. In a telephone system, a transmission line, a four-wire repeater circuit included therein, a source of current having a frequency F, a source of current having a frequency F, a receiving circuit responsive to current having a frequency F to connect current having a frequency F to the line,

' a receiving circuit responsive to current having a frequency F to connect current having a frequency F to the line, and

means effective when either of the frequencies F or F are connected to the line to change the connections of the repeater circuit to prevent singing.

12. In a telephone system, a fournvire repeater circuit, a transmission line conone end of said line and said repeater, comprising means for translating current of one frequency incoming to, current of another 4 frequency outgoing, and means actuated When one of said devices is operated to 2 change the circuit of the said repeater.

13. In a telephone system, a transmission line, a four-Wire repeater circuit connected thereto, a control circuit for said repeater, and relays in said control circuit selectively responsive to current transmitted via the repeater to change the circuit connections of the repeater circuit.

Inwitness whereof, We hereunto subscribe our names this 16th day of December, A. D., 35

RAY S. VVILBUR. EDGAR D. JOHNSON. 

